The proposed study concerns the organization of the myelin membrane and its alteration in disease. We are examining the metabolic turnover, formation, and interrelationships of the three classes of myelin proteins. The fractionation, isotopic, immunoradiometric, immunohistologic, and affinity chromatographic techniques applied to the membrane proteins will also be used to study tubulin, filarin, and the glial fibrillary acidic protein (GFA). Recent demonstration of the association of the GFA protein with the proteins of non-myelinated axons have prompted a reevaluation of the high molecular weight proteins found associated with purified myelin. We are studying the possible neuronal and glial origin of this fraction. An immunohistologic study at the light and electron microscopic levels of myelin basic protein, cerebrosides, and GFA protein in the rat optic nerve in the early stages of maturation is being carried out. BIBLIOGRAPHIC REFERENCES: S. K. Ludwin, J. C. Kosek and L. F. Eng. The Topographical Distribution of S-100 and GFA Proteins in the Adult Rat Brain. J. Comp. Neurol. 165, 197-208, 1976. L. F. Eng, Y. L. Lee and L. E. M. Miles. Measurement of glial fibrillary acidic protein by a 2-Site immunoradiometric assay. Anal. Biochem., April 1976. In press.